This disclosure relates generally to a control system and more particularly to a ballast control for a light source treatment system of fluids such as an ultraviolet (UV) treatment of water commonly used in a home water treatment system.
It is known in the art that UV light sources can be used to treat or disinfect/sterilize water such as described in commonly owned U.S. Pat. No. 6,057,917, the disclosure of which is incorporated herein by reference. Low-pressure mercury vapor discharge lamps, for example, have been widely used for many years for this purpose. Ultraviolet disinfection systems typically expose water to UV radiation (light) such that the radiation passes through the water and advantageously doses any microorganisms in the water. The UV radiation or light disrupts the DNA of the microorganisms which impacts on reproduction and thereby renders the microorganisms harmless. Of course, the intensity and duration of the UV exposure can impact whether a proper dose of UV radiation is provided to assure adequate treatment of the water.
Typical systems keep the ultraviolet source, usually a lamp, in the “on” condition at all times. This insures that the water is always disinfected whether there is high or low flow through the system, and even if there is no flow in which case the standing water and any potential microorganisms therein are continuously dosed by the emitted UV light. It will be appreciated, however, that if water demand is infrequent and there are long periods of time where there is often standing water or low flow conditions, then the lamp is wasting energy. In addition, the always “on” lamp has a corresponding shorter system life.
Another problem with known systems is that a UV emitting lamp that is always “on” can unfortunately heat the water in the reactor/reservoir during low flow or static operation of the system. Generally, the undesired heating impacts on customer satisfaction. Further, the heating can cause the ultraviolet output to decrease, risking tripping the alarm on the UV intensity monitor.
Thus, a need exists to operate the UV lamp in a non-continuous manner in an effort to eliminate false alarms, prevent needless heating of the water, reduce energy costs, extend useful life of the UV lamp in the system, and still provide sufficient disinfection.
A problem with the non-continuous ultraviolet output systems is that a slow or gradual rise in bringing the lamp to an “on” condition when power is supplied to the lamp, can increase the risk of passing contaminated water through the system. That is, insufficient exposure of the water to the UV could occur as the lamp is warming up, and the system otherwise permits the water to leave the reservoir without a desired level of UV dosing.